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CHAPTER 7: The Evolution of Living Things
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Section 7.1 Change Over Time
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Adaptation
• A characteristic that helps an organism survive and
reproduce in their environment (may be physical or
behavioral)
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Species
• Group of individuals that can mate (reproduce) only
among themselves to produce offspring
• Groups of individuals of same species living in
same place make up a population
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Species
• Species evolve over time by passing on genetic info
• Individuals in a population do not evolve – species
as a whole does
• Either survive the conditions they encounter or they
will die
• Cannot change due to pressure put on them by the
environment
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Species
• When born possess genetic traits that determine if
they can survive and reproduce because it had
useful traits (over time more and more useful traits
are passed on)
• Useless traits are also passed but not possessed by
all individuals since not “selected” for
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Evolution
• Populations gradually changing over time – thus
new species are formed.
• New species descend from older ones
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Evolution Misconceptions
• Man did not come from monkey - we share a
common ancestor
• A fin will not turn into an arm but a will see a fin
turn into a better fin over time (ie. a structure will
become more useful over time)
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Fossils
• Remains, imprints, or traces of once living
organisms (usually preserved in rock) that tell
us when, where, and how these organisms
lived
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Fossils
• Can be complete organisms or parts of organisms or
just a set of footprints
• Usually form when a dead organism is covered by a
layer of sediment; minerals replace organism with
stone
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The Fossil Record
• Timeline of life
• Organizes fossils by their estimated ages & physical
similarities
• Examine fossil record to figure out relationships
between extinct and living organisms.
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• The
geologic
time scale
Table 14.1
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Skeletal Structures
• Structure and order of bones of the human arm are
similar to those front limbs of cats, bats, and whales
(limbs are different sizes because they perform
different functions)
• Suggests that all these organisms shared a common
ancestor at some point in time.
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Homologous Structures
– Same bones in each organism even though they perform different functions
Human
Cat
Whale
Bat
Figure 13.10
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DNA
• Species that have similar traits evolved from a common
ancestor and therefore will also have similar DNA.
• Species that share a more common ancestor have fewer
amino acid differences
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Section 7.2 How Does Evolution Happen?
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Darwin
– Charles Darwin –
naturalist (studied nature).
– Explained how evolution
happens.
– Hypothesized that the
finches (over many
generations) may have
adapted to diff. ways of
life (finding food, space to
live) on the islands.
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The Voyage of the Beagle
– Collected thousands of specimens
– Observed various adaptations in organisms
Great
Britain
Europe
North
America
PACIFIC
OCEAN
ATLANTIC
OCEAN
Africa
Galápagos
Islands
Equator
South
America
Australia
Cape of
Good Hope
Tasmania
Cape Horn
Tierra del Fuego
New
Zealand
Figure 13.3
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Darwin
– Studied finches in the Galapagos Islands.
– Discovered that finches differed on each island (they
seemed similar but yet had so many diff. adaptations).
(a) Large ground finch
(b) Small tree finch
(c) Woodpecker finch
Figure 13.13
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Selective Breeding
• Human practice of breeding animals/plants that
have certain desired characteristics (genetic traits).
• Ex. People breed dogs with good hunting skills or
horse with great speed.
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Population
• Humans have potential to reproduce rapidly – food
supplies cannot support an unlimited population.
• Human populations are limited by choices we make
or by starvation and disease.
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Population
• Darwin realized any species can produce many
offspring and that these populations were limited by
starvation, disease, predation, competition. (only
limited # of individuals survive to reproduce).
• Thus offspring inherit traits that help them survive
in their environment.
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Natural Selection
 Process by which individuals better adapted to their
environment survive & reproduce more than less
well adapted individuals do (some genes make an
organism more likely to survive to reproduce).
 Individuals with certain heritable (favorable) traits
leave more offspring than others
 Natural selection explains how a population
changes in response to its environment because
these favorable characteristics will increase in the
population.
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Section 7.3 Natural Selection in Action
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Natural Selection in Action
• Examples of natural selection include
– Changes in a population sometimes observed when new force
affects survival of individuals – ex. Hunting elephants (tusks
vs. tuskless)
– Resistance = some insects and bacteria are now resistant to
chemicals/drugs that at one time killed them.
– Insects can become resistant because have short generation
times (period between birth of one generation & birth of next
generation).
– Finding a mate is part of struggle to reproduce (competition
occurs)
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Examples of Evolution in Nature
• Industrial Melanism
– Peppered months (white & blends in on birch tree)
but pollution lead to dark moths begin more common
in industrial areas (moth adapted to environment)
• Finch Beaks
– Birds evolved in diff. ways to adapt to food sources
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Speciation
• Speciation = formation of new species as result of
evolution.
1. Separation – part of population becomes separated
from original population
2. Adaptation – over time the two populations adapt to
their diff. environments and evolve diff. traits
3. Division - can no longer reproduce w/each other and
are not same species anymore
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• In branching
speciation, one or
more new species
branch from a parent
species that may
continue to exist
(b) Branching
evolution
Figure 14.2b
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Section 8.3 Humans & Other Primates
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The Evolution of Primates
• Primates are a group of mammals that include
humans, apes, monkeys, and lemurs.
• Primate evolution
– Helps explain human origins
– Humans and apes have shared a common ancestry
about 5–7 million years ago
– “Lucy” best preserved skeleton of prehuman hominid
(3 mya)
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Human
Gibbon
Old World monkey
Orangutan Gorilla
Chimpanzee
Figure 13.12
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• Primate characteristics include
– Limber shoulder
joints
– Eyes in front of the
face
– Excellent eye-hand
coordination
– Extensive parental
care
– Opposable thumbs
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Figure 17.39
Chimpanzee fetus
Human fetus
Chimpanzee adult
Human adult
Figure 14.17
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Ape vs. Human Skeleton
• Ape
– “C” shape spine, arms longer than legs, narrow
pelvis, smaller brain, quadraped
• Human
– “S” shape spine, arms shorter than legs, bowl
shaped pelvis, large brain, biped
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Modern Humans
• Humans are Homo sapiens (means wise man)
• Homo sapiens are only 34,000 years old
• Can walk upright
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings